Devices in advanced microelectronics employ silicon-on-insulator (SOI) technology for improved performance, where the active area of a device is in a thin silicon layer, isolated from the bulk silicon substrate by a buried oxide (BOX) layer. The BOX provides electrical isolation from the substrate for improved field distribution in the active area, but it also forms a major barrier for heat to dissipate from devices under severe operating or stress conditions down to the substrate. As a result, the devices of interest are at significantly higher temperature than the ambient or substrate temperature.
More specifically, a device such as a FET is built on a substrate and, as is well known, includes a channel, gate and oxide material. Within the channel to gate junction, self-heating is evident, typically occurring due to source voltage Vs, drain voltage Vd, and gate voltage Vg. For example, as the voltages are applied to the source, gate and drain of the device, internal heating begins to occur, typically which are non-uniform in distribution and degree. During the operational states of the circuits, the self-heating is also known to be non-uniform throughout the topology of the circuit.
Knowing the exact device temperature under a specified condition is critical in characterizing and modeling the device and its reliability. In one methodology, the device temperature is indirectly calculated by temperatures of the monitor devices at various distances from the device of interest. However, it is well known that the device temperature depends on the environment (such as the RX area, STI location, the number of nearby metal contacts/wires, etc) around the device of interest. Therefore, the temperature obtained using this method is only valid for the particular device measured with a given configuration and environment. This estimated temperature, of course, may be quite different from that of a different device of interest.
Also, various models are utilized to estimate the generated heat such as the Berkeley Short-channel IGFET Model for MOS transistors (BSIM). The BSIM model approximates the internal operations of a circuit at a certain design stage. These models use parameters of the circuit components to assist in the design of the final integrated circuit using mathematical statistical models. Although the BSIM is a good method to approximate the internal temperature of the integrated circuit, using approximations and statistical models only produce estimated results which cannot accurately account for the variations in temperature throughout the cross sections of the final integrated circuit product.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.